1. Field of Invention
The present invention relates to optical components and projectors containing the optical components. More specifically, the present invention relates to an optical component including an electro-optical device, a retaining frame which retains the electro-optical device, a prism, and a fixing pin for fixing the retaining frame and the prism, and to a projector containing the optical component.
2. Description of Related Art
Recently, projectors have become increasingly common, and are used in, for example, presentations at in-house conferences or at business trips. In addition, the projectors are also used in technical review sessions in research and development departments, etc., for projecting enlarged images of CAD/CAM/CAE data, in various seminars or workshops, or in classes in schools adopting audiovisual education. Furthermore, the projectors are also used for aiding discussions regarding medical treatments or medical education by projecting medical images and data of CT scans, MRI, etc., or for effectively conducting exhibitions or events wherein many people gather, etc.
Since the projectors are used in various situations as described above, the projectors must comply with various different specifications and functions. Accordingly, projectors have been developed which are compact and light, which enhances portability. Projectors have also been developed to have high resolution and high luminance, which enhances image quality, and to be highly functional, which provides connections to digital devices or to mobile devices.
It is expected that the projectors will be used in even more situations. Thus, projectors having additional specifications and functions are also being developed in prospect of the new situations in which they might be used.
With respect to the types of projectors described above, a projector is known in the art which includes an electro-optical device which modulates a plurality of colored lights in accordance with image information, a cross-dichroic prism which synthesizes the lights modulated by the electro-optical device, and a projection lens which enlarges and projects the lights synthesized by the cross-dichroic prism.
In such a projector, in order to reduce the size thereof, and to make the construction thereof simple, three light modulation devices (for example, liquid crystal panels), which form the electro-optical device, are fixed to the cross-dichroic prism with fixing members therebetween. Such a construction is suggested in, for example, Japanese Unexamined Patent Application Publication No. 11-25345 (applied by the present Applicant). According to this publication, a retaining frame, which retains a light modulation device, is provided with holes at four comers thereof, and fixing pins are inserted through the holes and are fixed to the holes. The ends of the fixing pins are adhered directly on a side surface of the cross-dichroic prism, so that the light modulation device is fixed to the cross-dichroic prism.
In the above-described construction, however, the ends of the fixing pins are adhered directly on the side surface of the cross-dichroic prism, so that the side surface of the cross-dichroic prism must have areas on which the fixing pins are adhered. Thus, a problem arises that the size of the dichroic prism must be large enough to provide the adhesion areas. Accordingly, even though the construction of the cross-dichroic prism can be made simpler, the size thereof cannot be reduced. More specifically, the size of the cross-dichroic prism cannot be reduced to the minimum size required from an optical point of view.
In order to reduce the size of the cross-dichroic prism, the size of the adhesion areas between the cross-dichroic prism and the fixing pins may be set to a minimum value. However, when the size of the adhesion areas is set to the minimum value, the adhesion strength between the cross-dichroic prism and the fixing pins may not be sufficient, and thus the fixation strength between the cross-dichroic prism and the light modulation device may not be sufficient either.
It is therefore an object of the present invention to provide an optical component and a projector in which the light modulation device is reliably fixed relative to the prism, and in which the size of the prism can be reduced to the minimum size required from an optical point of view.
In order to attain the above-described object, an optical component according to the present invention is constructed as described below.
In accordance with the present invention, an optical component includes a light modulation device; a retaining frame which retains the light modulation device; a prism; a fixing pin that fixes the retaining frame to the prism; and a frame member which is attached to a surface of the prism. In addition, one end of the fixing pin is fixed to the retaining frame, and the other end of the fixing pin is fixed to the frame member.
Accordingly, the frame member is attached to the prism, and the retaining frame, which retains the light modulation device, is attached to the frame member with the fixing pin. Thus, it is not necessary to fix the fixing pin directly to the prism, and the prism is not required to provide an area for fixing the fixing pin. Accordingly, the size of the prism may be reduced to the minimum size required from an optical point of view, and the prism may be made to be small.
In addition, since the fixing pin is fixed to the frame member, the area for fixing the fixing pin may be increased, irrespective of the size of the prism, by increasing the size, especially the width, of the frame member. Accordingly, sufficient fixation strength may be provided between the fixing pin and the frame member, and the light modulation device is reliably fixed relative to the prism.
In accordance with another aspect of the invention, the peripheral size of the frame member is larger than the surface of the prism to which the frame member is attached.
Since the peripheral size of the frame member is larger than the surface of the prism, the frame member only slightly covers the surface of the prism, and the area for fixing the fixing pin may be increased irrespective of the size of the prism. Thus, the fixing pin is reliably fixed relative to the prism, so that the light modulation device is also reliably fixed relative to the prism.
In accordance with another aspect of the invention, the retaining frame is formed of a synthetic resin, the prism is formed of an optical glass, and the frame member is formed of a metal.
The retaining frame, which is formed of a synthesized resin, and the prism, which is formed of an optical glass, are commonly used in optical devices such as projectors. Thus, the optical component may be constructed economically. In addition, since the frame member is formed of a metal, the frame member may be easily formed into a desired shape by using sheet metal, etc.
Furthermore, when the optical component is contained in, for example, a projector, the retaining frame and the prism may expand due to heat which occurs from a light source. The retaining frame is often formed of a plastic, and has a larger coefficient of thermal expansion compared to the prism. Thus, in the conventional optical component, there is a risk in that the retaining frame will expand at a larger rate compared to the prism while the projector is being used. In such a case, the relative position between the retaining frame and the prism will be changed, so that the relative position between the light modulation device and the prism will also be changed. In the present invention, the retaining frame, which is formed of a synthetic resin, and the prism, which is formed of an optical glass, are connected to each other via the frame member, which is formed of a metal having a coefficient of thermal expansion that is between the coefficients of thermal expansion of the synthetic resin and glass. Thus, even if heat occurs when the projector is used, any impact caused by the difference in coefficients of thermal expansion between the prism and the retaining frame may be compensated for to some extent by the frame member. Accordingly, the change in the relative position between the retaining frame and the prism due to the difference in coefficients of thermal expansion may be suppressed.
In accordance with another aspect of the invention, the frame member is provided with a film-receiving portion to which an optical film is attached.
Since the frame member is provided with the film-receiving portion, the optical film may be easily attached to the frame member. The optical film may be, for example, a retardation film, a polarizing film, or a wide view angle film.
In accordance with another aspect of the invention, an air gap is provided between a surface of the film-receiving portion, to which the optical film is attached, and the surface of the prism, to which the frame member is attached.
Since the air gap is provided between the surface of the film-receiving portion of the frame member, to which the optical film is attached, and the surface of the prism, the optical film may be disposed relative to the prism with a predetermined clearance therebetween. Accordingly, the air permeability between the optical film and the prism may be ensured.
In accordance with another aspect of the invention, an optical component includes a light modulation device; a retaining frame which retains the light modulation device; a prism; and a fixing pin that fixes the retaining frame to the prism. In addition, one end of the fixing pin is fixed to the retaining frame, and another end of the fixing pin is fixed to the frame member. The cross-section of the other end of the fixing pin is larger than the cross-section of the one end of the fixing pin.
Accordingly, the cross section of the other end of the fixing pin, which is adhered relative to the prism, is set to a relatively large value. More specifically, the end surface, which is the adhesion surface, at the other end of the fixing pin is set to a relatively large value. Thus, the adhesion strength between the fixing pin and the prism is more reliably ensured. The other end of the fixing pin may be adhered directly on the prism, or be adhered on the frame member as discussed above, as long as it is adhered relative to the prism.
On the other hand, a projector according to the present invention has the following construction in order to attain the above-described object.
In accordance with the invention, a projector includes a light modulation device which modulates a plurality of colored lights in accordance with image information; a prism which synthesizes the lights modulated by the light modulation device; and an optical component as discussed above. The lights synthesized by the prism are enlarged and projected so as to form a projection image.
Since the projector includes the optical component as discussed above, the adhesion strength between the prism and the fixing pin is ensured, and the size of the prism may be reduced. Accordingly, the size of the projector may also be reduced.
In accordance with another aspect of the invention, the projector further includes a power source which supplies electricity to the light modulation device.
Since the projector is provided with the power source which supplies electricity to the light modulation device, the light modulation device is easily supplied with electricity.